Communication access schemes using satellite connections are commonly accomplished by FDMA (i.e., Frequency Division Multiple Access) and TDMA (i.e., Time Division Multiple Access) processing techniques. Often the uplink signal is transmitted to the destination by the satellite utilizing bent pipe techniques meaning that the satellite performs merely as a repeater without performing any on-board switching or multiplexing function. Hence all switching and associated control must be performed at transmitting and receiving end stations on the ground. This limits the flexibility of the system since the intelligence of the system is concentrated in the ground end stations. CDMA is also used in satellite applications but the previous lack of satellite on-board processing has prevented the invention of hybrid systems that use different types of air interfaces for the uplink and downlink.
Traffic in systems such as voice/multimedia tends to be bursty in nature; a circumstance not favorable to TDMA and FDMA modes of transmission. Using a TDMA and FDMA mode of transmission is unsatisfactory because the assignment of time slots and/or frequency channels requires a setup time that is unacceptable in many applications. Also, changing the allocation of slots/frequency to meet transient demands is a complex process resulting in complex system control.